1. Field of the Invention
The present invention relates to an apparatus for driving a turntable of a disc player system, and more specifically to an apparatus for driving a turntable, having power sources for a normal and a reverse direction rotation of a spindle motor and a control circuit for controlling the supply of the power voltage from one of the power sources.
2. Description of Prior Art
In disc player systems such as a video disc player system and a compact disc player system, it is necessary to appropriately control the speed of rotation of a turntable depending on various modes of operations of the disc player system, including a stop mode in which the speed of rotation of the turntable should be decelerated relatively rapidly. In order to realize a sufficient deceleration, a driving voltage of an inverse polarity is generally applied to the spindle motor after the generation of a stop command signal so that the driving force of the reverse direction is applied to a rotor of the spindle motor. When the speed of the spindle motor has sufficiently dropped by this driving force of reverse direction, the supply of the driving voltage is stopped and the spindle motor is made coasting, or in other words, put into a free-running state.
For detecting the speed of the spindle motor, conventional apparatuses for driving a turntable are equipped with a frequency generator connected to the shaft of the spindle motor and peripheral circuits for determining the speed of the spindle motor from an output signal of the frequency generator. However, a drawback of the conventional apparatuses was that the reference speed of the spindle motor at which the driving of the motor is stopped and the spindle motor starts to coast was set relatively high due to the necessity of maintaining the stability of the circuits. Therefore, a long time was needed before the spindle motor stops completely. Further it was not easy to obtain a signal indicative of the complete stoppage of the spindle motor.